Neutron source



July 12, 1966 s. AMIEL ET AL NEUTRON SOURCE Filed June a, 1962 Anon/mes. 0e A/IAZd/V Me 02 .SAAD/A HIV/EL 057204;; 64 54; @weffyrn/ United States Patent 3,260,847 NEUTRON SOURCE Saadia Amiel and Aharon Nir, Rehovoth, Israel, assignors to Yeda Research and Development Co., Ltd., Rehovoth, Israel, a company of Israel Filed June 5, 1962, Ser. No. 200,258 Claims priority, application Israel, June 6, 1961, 15,593 4 Claims. (Cl. 250-845) It is an object of the present invention to provide a novel neutron source. It is a further object of the present invention to provide a novel neutron source which is characterized in that the flow of neutrons from same can be started and interrupted at will. Other and further objects of the invention will become apparent hereinafter.

The present invention relates to improved alpha-neutron sources, i.e. neutron sources comprising an emitter of a-particles (for short a-Cmiiifil) and a target material capable of emitting neutrons upon incidence of the uparticles.

In known neutrons sources of this type the solid atemitter and target are intimately intermixed and in some cases even compounded together, or provided in the form of an alloy. The reason for this is that the neutron yield of the source is increased by the intimate intermixing of the alpha emitter and the target.

Examples of target materials used in known alpha-neutron sources are Li, Be, B and F.

It is a drawback of known alpha-neutron sources that they incessantly emit neutrons and accordingly special precautions have to be taken during storage of such neutron sources.

The alpha-neutron emitter according to the invention comprises a radioactive emitter of tat-particles having an energy of at least 4 mev. and an oxygenous target mate rial enriched in 0 means being provided for bringing at will the source and the target to such a proximity as to set off neutron emission and means being provided to sever them at will so as to interrupt the neutron emission.

Particularly eflicient n-sources are obtained where the target material contains at least 50% of 0 calculated on the total content of oxygen.

The target material of the neutron source according to the invention may be solid, liquid or gaseous.

Examples of solid materials are oxides in which the metal may, if desired, be chosen from the group of metals capable of emitting neutrons upon incidence of tat-particles. An example of such a metal is beryllium and the target would in such a case be Be O A suitable liquid target is H O or water enriched in respect of 0 Suitable gaseous targets are 0 as well as gaseous compounds, containing 0 e.g. C0

As this invention may be embodied in several forms without departing from the spirit and essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them and all changes that fall within the metes and bounds of the claims, or of forms that are their functional equivalents are therefore intended to be embraced by these claims.

A fuller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing, in which FIGURE 1 is an elevational schematical cross-sectional 3,260,847 Patented July 12, 1966 ice view through an alpha-neutron source according to the invent-ion.

In this figure, 11 is a glass bulb of about 2 cm. diameter, in communication with an inlet-tube 12, provided with a stopcock 13, and an outlet tube 14, provided with a stopcock 15. Into bulb 11 there is introduced through opening 16 a carrier rod 17, coated at its lower end with a coating of a radioactive emitter 18 of alpha-particles of suit-able energy. Into this bulb 11 there is introduced an oxygenous liquid 19, such as water, enriched in 0", resulting in the commencement of an emission of neutrons. When it is desired to interrupt the flow of neutrons, the oxygenous liquid is removed from bulb 11 through stopcock 15.

Some quantitative data can be had from the following illustrative examples:

Example 1 About 1 curie of Th in equilibrium with its decay products is introduced into a glass tube and covered with 2.0 cc. of water in which the 0 content amounts to of the total oxygen. This source will emit approximately 3.10 neutrons per second. When no neutron emission is required, the thorium can be separated from the water by mere distillation or displacement of the water by means of an inert liquid and the two way components of the neutron source can be stored separately.

Example 2 About 10 me. of P0 is deposited on a Pt-wire and enclosed in an evacuated glass tube measuring about 2 cm. in diameter and comprising a control-valve for the admittance and discharge of gas. Pure oxygen gas cont-aining of 0 is introduced into the tube through the valve.

This alpha-neutron source will emit about 5.10 neutrons per second. The neutron emission can be interrupted by evacuating the oxygen through the valve.

What we claim is:

1. A neutron source comprising a container, a solid radioactive emitter of tat-particles which have an energy of at least 4 mev., means providing said radioactive emitter of a-particles in the interior of said container, a fluid oxygenous target material enriched in O atoms filling at least a portion of said container and in contact with said radioactive emitter of u-particles, and valve means extending through the wall of said container for draining said fluid oxygenous target material from said container, thereby to sever the said a-emitter from said target to interrupt neutron emission at will.

2. A neutron source comprising a container, a solid radioactive emitter of a-particles which have an energy of at least 4 mev., means providing said radioactive emitter of tat-particles in the interior of said container, a fluid oxygenous target material enriched in O atoms filling at least a portion of said container and in contact with said radioactive emitter of tat-particles, and valve means extending through the wall of said container for draining said fluid oxygenous target material from said container, thereby to sever the said a-emitter from said target to interrupt neutron emission at will, and second valve means in said wall of said container for admitting said fluid oxygenous target material into said container.

3. The neutron source substantially as set forth in claim 2, wherein said fluid comprises water having an O content enriched to approximate 80% of the total oxygen of said water.

4. The neutron source substantially as set forth in claim 2, wherein said fluid comprises oxygen gas containing approximately 90% of 0 References Cited by the Examiner UNITED STATES PATENTS 1/1959 Reardon et a1. 4/1959 Birden.

OTHER REFERENCES Nuclear Science Abstracts: vol. 14, March-April 1960,

4 Abstract No. 5900 (on page 747); vol. 15, JulyAug. 1961, Abstract No. 17390 (on page 2252); vol. 12, Jan.- March, 1958, Abstract No. 1715 (on page 190); vol. 13, Nov.Dec. 1959, Abstract No. 20, 105 on pp. 2698 and 2699.

TID295 Bibliography of Published Literature on the Preparation and Properties of Radioactive Neutron Sources, March 3, 1950 Technical Information Division ORE, United States Atomic Energy Commission, Oak Ridge, Tenn., page 28 refers to the Roberts article.

REUBEN EPSTEIN, Primary Examiner. CARL D. QUARFORTH, Examiner. 

1. A NEUTRON SOURCE COMPRISING A CONTAINER, A SOLID REDIOACTIVE EMITTER OF A-PARTICLES WHICH HAVE AN ENERGY OF AT LEAST 4 MEV., MEANS PROVIDING SAID RADIOACTIVE EMITTER OF A-PARTICLES IN THE INTERIOR OF SAID CONTAINER, A FLUID OXYGENOUS TARGET MATERIAL ENRICHED IN O18 ATOMS FILLING AT LEAST A PORTION OF SAID CONTAINER AND IN CONTACT WITH SAID RADIOACTIVE EMITTER OF A-PARTICLES, AND VALVE MEANS EXTENDING THROUGH THE WALL OF SAID CONTAINER FOR DRAINING SAID FLUID OXYGENOUS TARGET MATERIAL FROM SAID CONTAINER, THEREBY TO SEVER THE SAID A-EMITTER FROM SAID TARGET TO INTERRUPT NEUTRON EMISSION AT WILL. 